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Updated: Aug 8, 2026

Plunge Freezing: A Tool for the Ultrastructural and Immunolocalization Studies of Suspension Cells in Transmission Electron Microscopy
Published on: May 5, 2017
A novel method of natural cryoprotection : intracellular glass formation in deeply frozen populus
A G Hirsh1, R J Williams, H T Meryman
1American Red Cross, Biomedical Research Laboratories, Bethesda, Maryland 20814.
Abstract:
Correlating measurements from differential scanning calorimetry, freeze-fracture freeze-etch electron microscopy, and survival of twigs after two-step cooling experiments, we provide strong evidence that winter-hardened Populus balsamifera v. virginiana (Sarg.) resists the stresses of freezing below -28 degrees C by amorphous solidification (glass formation) of most of its intracellular contents during slow cooling (=5 degrees C per hour). It is shown that other components of the intracellular medium go through glass transitions during slow cooling at about -45 degrees C and below -70 degrees C. This ;three glass' model was then used to predict the results of differential scanning calorimetry, freeze-fracture freeze-etch electron microscopy, and biological experiments. This model is the first definitive explanation for the resistance of a woody plant to liquid N(2) temperatures even if quench cooling (1200 degrees C per minute) begins at temperatures as high as -20 degrees C and warming is very slow (=5 degrees C per hour). It is also the first time high temperature natural intracellular glass formation has been demonstrated.

